Refactor how we store and use samplers in Ganesh

src/effects/SkDisplacementMapEffect.cpp

Index: src/effects/SkDisplacementMapEffect.cpp
diff --git a/src/effects/SkDisplacementMapEffect.cpp b/src/effects/SkDisplacementMapEffect.cpp
index aee15ef753b0c9166f4b2224d6c31fff4a011491..973c760769fdd6bddcafaed0553243aab4b48171 100644
--- a/src/effects/SkDisplacementMapEffect.cpp
+++ b/src/effects/SkDisplacementMapEffect.cpp
@@ -551,8 +551,10 @@ void GrGLDisplacementMapEffect::emitCode(EmitArgs& args) {
 
     GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
     fragBuilder->codeAppendf("\t\tvec4 %s = ", dColor);
-    fragBuilder->appendTextureLookup(args.fTexSamplers[0], args.fCoords[0].c_str(),
-                                   args.fCoords[0].getType());
+
+    fragBuilder->appendTextureLookup(args.fUniformHandler->getSampler(args.fTexSamplers[0]),
+                                     args.fCoords[0].c_str(),
+                                     args.fCoords[0].getType());
     fragBuilder->codeAppend(";\n");
 
     // Unpremultiply the displacement
@@ -606,7 +608,7 @@ void GrGLDisplacementMapEffect::emitCode(EmitArgs& args) {
                             domain,
                             args.fOutputColor,
                             SkString(cCoords),
-                            args.fTexSamplers[1]);
+                            args.fUniformHandler->getSampler(args.fTexSamplers[1]));
     fragBuilder->codeAppend(";\n");
 }